Latest ArticlesPrecise and spatiotemporal control over the pesticide remains to be a challenge. More efficient controlled release systems (CRSs) have been developed to support the precise delivery of active ingredients. Herein, we incorporated the photoremovable protecting groups (PRPGs) into phenamacril (PHE) and obtained two photo-responsive fungicides of NV-PHE and DEACM-PHE. The 4,5-dimethoxy-o-nitrobenzyl (NV) or 7-diethylaminocoumarin (DEACM)-caged PHE could release the active molecule PHE after irradiation of UV light and blue light, respectively. Optical properties and in-vitro/vivo fungicidal activities of NV-PHE and DEACM-PHE demonstrated the feasibility for light controlled release of PHE. DEACM-PHE could release 98% PHE by illumination of blue light. The irradiated DEACM-PHE could preserve the similar bioactivity of PHE, and significantly improve the in-vitro/vivo fungicidal activities compared to the non-irradiated DEACM-PHE. The optical controlled release of PHE from DEACM-PHE enabled the precise and spatiotemporal delivery of PHE, diversifying the development of CRSs for pesticide, and providing environment-friendly agricultural applications with high pesticide efficiency.
Unraveling the catalytic reaction mechanism is a long-term challenge for developing efficient catalysts. The blooming bimetallic catalyst have enabled to activate inert bonds and realize complex C-C formation. Herein, we theoretically discover a dual-phosphinito bridged hetero-bimetallic species that verified by NMR experiments. Our results indicate only dual-phosphinito Ni-Al model can be an active catalyst in asymmetric cycloadditions via C-C activation and C-H activation, which can well rationalize the experimental observations for both reactivity and stereo-selectivity. An unprecedented tandem redox dehydrogenation mechanism was revealed to control the formation of this active species overriding the inherent basicity. Synergistic Lewis acid and eg orbital interactions, including dz2 orbital reoccupation and dx2-y2 orbital recombination, were disclosed to understand both thermodynamic and kinetic advance of dual-bridged model, displaying feasible redox properties.
Small-molecule hydrogels based on amino acid derivatives have promising applications in many biological fields, including cell culture, drug delivery, and tissue engineering. Although these hydrogels have been widely reported to have low cytotoxicity, biocompatibility, and tunable bioactivity, problems such as harsh preparation conditions and complex material design hinder their application. Herein, by adjusting pH to induce non-covalent interactions between small-molecule tryptophan derivatives (N-[(phenylmethoxy)carbonyl]-L-tryptophan, Mw: 338.35), we developed a self-assembled three-dimensional network hydrogel that can be rapidly formed in seconds. And the supramolecular self-assembly mechanism of the hydrogels was also investigated in detail through experimental characterizations and density functional theory calculation. As-prepared hydrogels also exhibit reversible pH-stimulated response and self-healing properties. This study details a research process for the simple and rapid preparation of tryptophan derivative-based hydrogels, which provides more reference ideas for the future development of materials based on other amino acid derivatives.
Carbon dots (CDs) with room-temperature phosphorescence (RTP) have attracted dramatically growing interest in optical functional materials. However, the photoluminescence mechanism of CDs is still a vital and challenging topic. In this work, we prepared CD-based RTP materials via melting boric acid with various lengths of alkyl amine compounds as precursors. The spatial effect on the structure and the RTP properties of CDs were systematically investigated. With the increase in carbon chain length, the interplanar spacing of the carbon core expands and crosslink-enhanced emission weakens, resulting in a decrease in the phosphorescence intensity and lifetimes. Meanwhile, based on triplet-to-singlet resonance energy transfer, we employed intense and long-lived phosphorescence CDs as the donor and short-lived fluorescent dyes as the acceptor to achieve long-lived multicolor afterglow. By the triplet-to-singlet resonance energy transfer, the afterglow color can change from green to orange. The afterglow lifetimes are more than 0.9 s. Thanks to the outstanding afterglow properties, the composites were used for time-resolved and multiple-color advanced anticounterfeiting. This work will promote the design of multicolor and long-lived afterglow materials and expand their applications.
Shortcut nitrification-denitrification (SCND) is widely concerned because of its low energy consumption and high nitrogen removal efficiency. However, the current difficulty lies in the stable maintenance of SCND performance, which leads to the challenge of large-scale application of this new denitrification technology. In this study, the nitrogen removal pathway from complete nitrification-denitrification (CND) to SCND was rapidly realized under high free ammonia (FA), high pH and low dissolved oxygen (DO) conditions. The variations of specific oxygen uptake rate (SOUR) of activated sludge in both processes were investigated by an online SOUR monitoring device. Different curves of SOUR from CND to SCND process were observed, and the ammonia peak obtained based on SOUR monitoring could be used to control aeration time accurately in SCND process. Accordingly, the SOUR ratio of ammonia oxidizing bacteria (AOB) to nitrite oxidizing bacteria (NOB) (SOURAOB/SOURNOB) was increased from 1.40 to 2.93. 16S rRNA Miseq high throughput sequencing revealed the dynamics of AOB and NOB, and the ratio of relative abundance (AOB/NOB) was increased from 1.03 to 3.12. Besides, SOURAOB/SOURNOB displayed significant correlations to ammonia removal rate (P < 0.05), ammonia oxidation rate / nitrite oxidation rate (P < 0.05), nitrite accumulation rate (P < 0.05) and the relative abundance of AOB/NOB (P < 0.05). Thus, a strategy for evaluation the SCND process stability based on online SOUR monitoring is proposed, which provides a theoretical basis for optimizing the SCND performance.
Anthropogenic carbon dioxide (CO2) emission from the combustion of fossil fuels aggravates the global greenhouse effect. The implementation of CO2 capture and transformation technologies have recently received great attention for providing a pathway in dealing with global climate change. Among these technologies, electrochemical CO2 capture technology has attracted wide attention because of its environmental friendliness and flexible operating processes. Bipolar membranes (BPMs) are considered as one of the key components in electrochemical devices, especially for electrochemical CO2 reduction and electrodialysis devices. BPMs create an alkaline environment for CO2 capture and a stable pH environment for electrocatalysis on a single electrode. The key to CO2 capture in these devices is to understand the water dissociation mechanism occurring in BPMs, which could be used for optimizing the operating conditions for CO2 capture and transformation. In this paper, the references and technologies of electrochemical CO2 capture based on BPMs are reviewed in detail, thus the challenges and opportunities are also discussed for the development of more efficient, sustainable and practical CO2 capture and transformation based on BPMs.
Owing to their unique design and development, high safety and low-cost efficient cathode is still at the forefront of research for rechargeable zinc-ion batteries. However, the suitable cathode operating with ultrahigh capacity with a dendrite-free anode reaction mechanism remains challenging. In this, the first archetype of a high-rate and morphologically stabled cathode material is constructed from novel cauliflower-like nano-ZnV2S4 for aqueous zinc-ion batteries. Thus, nano-ZnV2S4 was prepared with an anion exchange reaction using ZnV2(OH)8 cauliflower-like nanostructured array as a template interestingly no morphological and shape changes were detected. The as-prepared nano-ZnV2S4 electrode reveals a specific discharge capacity of 348.2 mAh/g during 0.5 A/g with enhanced rate capability and excellent capacity retention of 89.2% at 4 A/g current density even after completing 1000 cycles.
Circularly polarized light (CPL) is an inherently chiral entity and is regarded as one of the possible deterministic signals that led to the evolution of homochirality in earth. Thus, CPL as an external physical field has been widely used in a technique known as absolute asymmetric synthesis, because a product enriched in one enantiomer is formed from racemic precursor molecules without the intervention of a chiral catalyst. In this review, we retrospect the historical research of CPL-induced absolute asymmetric synthesis, including chiral organic molecules, helical polymers, supramolecular assemblies, noble metal nanostructures. However, based on these results, we concluded that the chiral photon-matter interaction is very faint due to the arrangement of molecular bonds giving rise to chiral features, is over a smaller distance than the helical pitch of CPL, leading extremely small enantiomeric excess for product. Therefore, we highlight the recently emerged technology called superchiral field, in which the superchiral far-field and near-field could enhance the dissymmetry of optical field and near-field, respectively. In sum, we hope this review could bring some enlightenment to researchers and further improve the enantioselectivity of CPL-induced absolute asymmetric synthesis.
π-Electron coupling of pendant conjugated segment in π-stacked semiconducting polymers always causes the formation of defect trapped sites and further quenched high-band excitons, which is harmful to the performance and stability of deep-blue polymer light-emitting diodes (PLEDs). Herein, considerate of “defect” carbazole (Cz) electromers in poly(N-vinylcarbazole) (PVK), a series of fluorene units are introduced into pendant segments (PVCz-DMeF, PVCz-FMeNPh and PVCz-DFMeNPh) to suppress the strong π-electron coupling of pendant Cz units and enhance radiative transition toward fabricating sable PLEDs. Compared to PVCz-FMeNPh and PVCz-DFMeNPh, PVCz-DMeF spin-coated films show a relatively efficient deep-blue emission, completely similar to its single pendant chromophore, confirmed an extremely weak charge-transfer and electron coupling between adjacent pendant segments. Therefore, PLEDs based on PVCz-DMeF present stable and deep-blue emission with a high color purity (0.17, 0.08), associated with extremely weak defect emission at 600~700 nm (induced by carbazole electromers). Finally, PLEDs based on PVCz-DMeF/F8BT blended films (1:1) also present the high maximum luminance (Lmax) of 6261 cd/m2 and current efficiency (CEmax) of 2.03 cd/A, confirmed slightly trapped sites formation. Therefore, precisely control the arrangement and packing model of pendant units in π-stacked polymer is an essential prerequisite for building efficient and stable emitter for optoelectronic devices.
Current clinical treatments cannot effectively delay the progression of osteoarthritis (OA). Consequently, joint replacement surgery is required for late-stage OA when patients cannot tolerate pain and joint dysfunction. Therefore, the prevention of OA progression in the early and middle stages is an urgent clinical problem. In a previous study, we demonstrated that NDRG3-mediated hypoxic response might be closely related to the development and progression of OA. In this study, an injectable thermosensitive hydrogel was established by cross-linking Pluronic F-127 and hyaluronic acid (HA) for the sustained release of hypoxia-induced exosomes (HExos) derived from adipose-derived mesenchymal stem cells. We demonstrated that for OA at the early and middle stages, the HExos-loaded HP hydrogel could maintain the chondrocyte phenotype by enhancing chondrocyte autophagy, reducing chondrocyte apoptosis, and promoting chondrocyte activity and proliferation through the NDRG3-mediated hypoxic response. This novel composite hydrogel, which could activate the NDRG3-mediated hypoxic response, may provide new ideas and a theoretical basis for the treatment of early- and mid-stage OA.
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